Cutting

 

Cutting

Fabric cutting means to cut out the garment pieces from the lays of fabric with the help of cutting template or marker. In other word, cutting is the process of separating garment parts from the fabric lay in precise size and shape.

 Requirements of fabric cutting:

To cut the fabric from the lay in desired size and shape, following requirements must be fulfilled:

 

Ø  Precision of cut.

Ø  Clean edges.

Ø  Unfused edges.

Ø  Support of the lay.

Ø  Consistent cutting.

 1.  Precision of cut:

                            Garments cannot be assembled satisfactorily and they may not fit the body shape correctly if they have not been cut accurately to the pattern shape. Precision of cut means cutting parts shape and size must be as per original sketch.

   It depends upon some factors:

 

Ø The method of cutting adapted

Ø The marker planning.

Ø Marker making/duplicating.

Ø Condition of the cutting machine.

Ø Skill ness and attentiveness of the operator.

 

2. Clean edges:

           Fabric edges should be smooth and clean, the raw edges of the fabric should not show fraying or snagging. If the knife is not sharp enough, such problems may occur.

 3. Unfused edges:

 

          The build up of heat in the knife blade comes from the friction of the blade passing through the fabric. This, in extreme cases, fuses the raw edges of thermoplastic fiber fabrics. The cutter cannot separate individual plies from the pile of cut parts. Forced separation causes snagged edges, and in cases hard edge is uncomfortable in wear.

      

         Remedies:

Ø  Use anti-fusion paper between the layers.

Ø  Use silicon lubricants on to the blade.

Ø  Spraying the blade with air coolant lubricant.

Ø  Slowing down the speed of the blade.

Ø  Reducing the height of the lay.

Ø  Use well sharpened blade.

 

5. Support of the lay:

 

Surface of the cutting table depends on the type of cutting technique adopted. Surface of the cutting table should be strong enough to bear the weight of cutting lay and allow the movement of the cutting machine. The cutting system must allow the blade to penetrate the lowest ply of the spread. If the lay is not supported, the cutting accuracy will be affected.

 

6. Consistent cutting:

Whatever cutting techniques may use, cutting should be consistent. Top to bottom ply of a lay should be in same size and shape. Both manual and mechanical faults may be responsible for inconsistent cutting.

 

       

 

Methods of cutting:

 

There are mainly three types of cutting techniques:

1.      Completely manual technique-Hand operated scissors.

2.      Manually operated powered knife

a. Straight Knife

b. Round knife

c. Band knife

d. Die cutter

e. Notcher

f. Drill

 

3.               Computerized technique.

       a. Knife cutting

       b. Cutting by water jet

       c. Laser cutting

       d. Plasma torch cutting

 

1. Manual technique:

 

           Various types of scissor are normally used when cutting only single or double plies. This technique is flexible enough to accommodate any fabric construction & pattern shape.

 

 Advantage:

 

Ø  Suitable for small production.

Ø  Easy to operate.

Ø  Used for tailoring & domestic purposes.

Ø  Used in garments manufacturing.

Ø  Suitable for making sample garments.

 

  Disadvantage:

 

Ø   Time consuming method.

Ø    High labor cost per garment.

Ø    Fabric wastage is very high.

Ø   Limitation to use in garments industry.

 

 

 

 

 

Straight Knife: widely used cutting machine which cut fabrics in bulk with high precision.

 

Features:

 

      Cutting knife is straight in shape.

                      Blade length= 08’’-13”

                      Blade width= (1 ½ -3) cm.

                      Blade thickness= ½ mm.

      Knife is driven by electric power.

      Grinding wheel is present to sharp the knife during cutting.

      The machine consists of base plate, electric motor, handle, knife, knife guard, stand, roller wheel.

      Base plate usually on roller wheel.

      Handle for the cutter to direct the blade.

      Most commonly (99%) used in garment industry of Bangladesh.

 

 

Machine description:

 

1.      An Electric motor.

2.      Base plate: Usually in rollers for ease movement.

3.      Handle: to direct the blade.

4.      Knife: reciprocating motion

5.      Knife guard

6.      Grinding wheel: To sharp the knife during cutting

7.      Stand.

8.      Roller wheel: To move the machine over cutting table easily

 

 

 

           

 

Working principle:

 

  Two kind of power are required to operate a straight knife.

 

·      Motor power drives the reciprocating blade.

·      Operator power drives the knife through the lay.

 

                 The motor power needed is determined by:

 

·  The height of the ply.

·  The construction of the fabric.

· The curvature of the line being cut.

·  The stroke of the blade.

 

         The greater the power of the motor, the heavier will be the machine. If the blade movement is faster, it cuts the fabric better. Operator effort is affected by the weight of the motor, the shape of the standard, handle weight, stroke, and sharpness of the blade and effect of the base plate rollers on the table surface.

 

Benefits:

§  High production cutting machine.

§  Possible to cut fabric directly.

§  Possible to cut larger height of the fabric lay.

§  Both sharp corners and heavy curves could be cut.

§  Blade could be sharpen by attaching grinding wheel during cutting.

§  High cutting speed.

§  Comparatively cheap.

 

 

Disadvantages:

§  Blade deflection occurs, so in some cases fabric cut pieces can be found faulty.

§  If depth of the fabric is higher, the possibility of deflection of the blade is more.

§  The machine is not ergonomic; Intensity of the accident is comparatively higher.

 

Precaution to avoid blade deflection: 

Ø  Reducing the lay height.

Ø  The weight of the motor should be light.

Ø  The operator should be skilled and conscious.

Ø  Speed of the machine may be reduced.

 

 

 

 

Factors considered for choice of cutting:

 

      Type of the fabric: Technique should be such as that it should not damage the fabric. In case of natural fiber fabric, all methods may be applied, but Laser and Plasma method is not suitable for Man Made Fiber fabric.  

      Accuracy of cutting: for higher accuracy, computerized method may be adapted & for lower accuracy, manual technique may be suitable.

      Available of cutting machine: which machine is available to suit the cutting technique.

      Volume of cutting: For small amount of cutting, round knife is suitable and for large volume of cutting, straight knife is suitable.

      Quality of cutting: Computerized cutting methods are suitable for high quality fabric cutting and manually operated powered knife is suitable for comparatively lower cutting quality.

      Time factor: For urgent requirement of fabric cutting, straight knife is more suitable as that technique requires comparatively less preparatory time.

 

Reasons of fused edge in cutting:

 

o   The build up of heat in the knife comes from the friction of the blade passing through the fabric.

o   If the fabric is made of thermoplastic fiber such as polyamide or polyester.

o   High ply height causes fused cutting edge.

o   If blade is not well sharpened, the cutting edge may be fused.

     Remedies:

       

      Use antifriction paper between the layers.

      Use silicon lubricants on to the blade.

      Height of the ply should be reduced.

      Slowing down cutting speed

      Use well sharpened blade.